1. Field to which Invention Relates
The invention relates to an installation and a method for producing cement in which a mixture of limestone and clay minerals are ground to form raw flour and the latter is calcined in a rotary kiln with the necessary supply of heat and fired to form clinker.
2. The Prior Art
In the case of prior art methods, the clinker produced has a temperature of approximately 1400.degree. C and must be cooled in coolers to temperature of 80 to 250.degree. C. This cooling requirement leads to an interruption of the production process because the clinker must be transferred from the rotary kiln to a clinker store for cooling. After this interruption the clinker can be ground in a mill with the addition of gypsum and other materials to form cement. The grinding is generally carried out in a cement tube mill.
For clinker cooling use is made of planetary coolers, tube coolers, shaft coolers or grate coolers. However, all clinker coolers have the disadvantage that, owing to the poor heat transfer from the lump clinker, very large amounts of cold air are necessary. If insufficient quantities of air for cooling are provided, the clinker is insufficiently cooled.
In the case of one application of planetary coolers, tube coolers or shaft coolers the quantity of cooling air is adapted to suit the air requirement of the rotary kiln. However, the clinker still remains too hot. As a result it must be subsequently cooled during intermediate storage and in the clinker grinding installation. The waste heat of the cooling air cannot usually be made use of.
In the case of grate coolers a quantity of cooling air is used which exceeds the requirement of the rotary kiln so that, although the clinker is cooled to a greater degree, the excessive cooling air must be separately freed of dust. There is also an attendant loss of heat.
The necessity, in the case, for the known methods of cooling the lump clinker material and the subsequent sacrifice as regards the interruption of production is a substantial economic disadvantage.
It had not been gathered that it is appropriate to comminute the clinker material for the cooling operation in order in this manner to increase the surface area for heat exchange.